code: def test_negative_labels():
      labels = np.array([0, -1, -2, 0])
      rout = np.array(
          [
              (0.0, 0.0, 0.0),
              (0.0, 0.0, 1.0),
              (1.0, 0.0, 0.0),
              (0.0, 0.0, 0.0),
          ]
      )
      assert_array_almost_equal(
          rout, label2rgb(labels, bg_label=0, alpha=1, image_alpha=1)
      )
  
imports: import itertools
  import numpy
  import pytest
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_no_warnings, assert_warns
  from skimage._shared.testing import expected_warnings
  from skimage.color.colorconv import hsv2rgb, rgb2hsv
  from skimage.color.colorlabel import label2rgb
label_desc: Use image node_id 10 for calling a global function with example usage: test_negative_labels() without return types